## Blow bubbles!

By David Shaw, 27 August 2013

Keen to blow some seriously big bubbles? Try making this bubble mix!

## You will need

You will need these items.

- Dishwashing detergent
- Glycerine
- Water
- Large jar
- Measuring jug
- Bendable wire, such as large paperclips
- Pliers

## Make bubble mix

- Measure the volume of your jar. You can do this by filling the jar with water and then using a measuring jug to measure the water in mL.
Calculate how much of each ingredient you will need.

- To use the recipe, first work out how much bubble mix you want. Pick a volume slightly less than the volume of your jar.
- This recipe is written as percentages. For each ingredient, multiply the percentage by the volume you picked. The recipe is:

- 30% dishwashing detergent
- 10% glycerine
- 60% water

- To check you’ve got the right quantities, add up the volumes in mL that you calculated for all three ingredients. They should add up to the volume of bubble mix you picked.
Mix all the ingredients in a jar.

- Pour all the ingredients into a jar and stir the mix carefully. Your bubble mix is now ready!

## Blow bubbles!

- Bend your wire into a straight line.
- Bend the end part of the wire into a square. Make sure the square will fit into your jar and that you have some wire coming off the square as a handle to hold with the pliers.
- Use the pliers to dip the square into your bubble mix and pull it out again. There should be a thin film of bubble mix inside the square.
- Softly blow through the film and you should make bubbles. Are they square like your frame?
Bend the paperclip into a square.

## What’s happening?

This bubble mix is a combination of many different chemicals, including water, surfactants and sugars. The molecules in bubble mix are attracted to each other. This attraction is why films of bubble mix stay together, instead of breaking up into drops.

Since bubble mix is attracted to itself, it’s always trying to make the smallest shape it can. Normally that would be a single drop, but a bubble has air trapped inside. The bubble mix tries to shrink around the air and ends up in a sphere shape. This is a ‘minimal surface’ – the shape with the smallest surface area.

Blow softly through the square to make a bubble!

If you blow a lot of bubbles, you might get two bubbles stuck together. Each bubble will look like a sphere with one flat side. This isn’t a minimal surface for the individual bubbles, but the flat side is shared so there’s actually less bubble film than there would be with two separate bubbles!

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